Process for capillary electric welding of low and high alloy steels, hardened or not, and bimetals, for the obtainment of a determined texture, without thermal treatment

ABSTRACT

Patent of Invention for PROCESS CAPILLARY ELECTRIC WELDING OF LOW AND HIGH ALLOY STEELS, HARDENED OR NOT, AND BI-METALS, FOR THE OBTAINMENT OF A DETERMINED TEXTURE, WITHOUT THERMAL TREATMENT, in which the first layer ( 1 ) is used to line the bevel and its root with electrodes of crystallization of the deposited welding material, said weld being adequate for the obtainment of the austenitic plus ferretic texture. With the second layer ( 2 ), proceed with the filling of the bevel with the crystallization of the deposited weld, obtaining a perlitic or pearlitic plus troostitic texture, while in the third and fifth layers ( 3, 5 ), the electrode for the obtainment of an austenitic plus ferritic texture. In the fourth layer ( 4 ), the electrode of deposited weld crystallization for the obtainment of a sorbitic plus bainitic texture is used, and in the sixth layer ( 6 ), an electrode for deposited weld crystallization for the obtainment of a bainitic texture is used.

The present report discusses a process for capillary electric welding of low and high alloy steels, hardened or not, and bimetal, for the obtainment of a determined texture, without thermal treatment

As it is known by technicians on the subject, when welding hardened steel, low and high alloy steel, forged steel with high carbon content, bimetallic union (for example, welding of two different metals, such as stainless steel with carbon steel), manganese steel, Hadfield steel and others, a conventional thermal treatment system is necessary before, during and/or after a weld, in order to normalize the undesirable crystallization of the weld applied, martensitic and thick, which is found in the so-called Affected Transition Zone, or Thermally Affected Zone. This thermal treatment significantly increases the cost of the final product.

Furthermore, the size of the piece frequently impedes the thermal treatment and, therefore, the welded part becomes very hard and does not meet the requirements of dynamic strength of the part, resulting in fissures and cracks, sometimes resulting in its breakage. The low temperature welding process used to weld all types of steel, their alloys, bi-metals and, also, cast pieces, presented by this invention, includes the selection of the appropriate crystallization of the welding material deposited, the system of electrode application and the correct use of the deposited weld, with the observance of the temperature of the part during the welding operation, in order to eliminate the undesirable thick martensitic texture and avoid the recrystallization of the Weld Transition Zone, also known as Affected Transition Zone (ATZ).

The new process of the present invention includes four types of electrodes for the selection of the adequate weld crystallization deposited, such as the austenitic plus ferritic; pearlitic or pearlitic plus troostitic; sorbitic plus bainitic; and bainitic. These electrodes have never been used to weld hardenable steels or Hadfield steel, high carbon steel, high alloy steel and bi-metals, without thermal treatment.

In this way, the mechanical and physical characteristics of the base material are preserved and the deposited weld is machineable which permits that more important mechanical designs be modified for the use of alloy steels of the types SAE 4140, 4330, 4345, among other types of steel.

The present process known as “low temperature welding”, eliminates thick martensitic texture and avoids the recrystallization in the Weld Transition Zone, also known as the Affected Transition Zone (ATZ), and eliminates any type of thermal treatment, without hardening the deposited weld and not altering the physical characteristics of the base material, thus permitting the machining of the deposit material, due to the absence of the thick martensitic crystals and, consequently, adequate hardness of the deposited metal.

The invention is described in detail below regarding the preferred manner of execution and shown in the attached drawings.

FIG. 1 illustrates a union made in accordance with the proposed invention;

FIGS. 2 to 13 illustrate the different layers of deposit in the bevel; and

FIGS. 14 to 29 illustrate how the intercalation of the weld beads is executed.

The invention consists in the use of capillary electric welding electrodes with specific characteristics for all types of steel, such as low and high alloys and hardenable or hardened steels, high carbon steel or manganese steel (Hadfield) or SAE 4140 steel, the parts requiring beveling according to the X, U or V bevel pattern, independent of their thickness, it being unnecessary to know the chemical composition of the material or materials to be welded, such as in the case of unlike parts like bi-metals.

The welding of a part is started (7), after being duly beveled, using an austenitic and ferritic weld deposit crystallization type electrode, as follows:

In the 1^(st) layer (1), both sides of the bevel are covered, including its root, using electrodes with adequate weld crystallization to obtain the austenitic plus ferritic type structure, tacking the parts to join them with the same electrode.

In the 2^(nd) layer (2), an electrode with the adequate crystallization for the obtainment of the pearlitic or pearlitic plus troostitic texture is used. In the 3^(rd) layer (3), the electrode with the adequate weld crystallization is deposited for the obtainment of the austenitic type texture, and in the 4^(th) layer (4), an electrode with the adequate weld crystallization is deposited for obtainment of the sorbitic plus bainitic type texture.

In the 5^(th) layer (5), an adequate crystallization welding electrode is used for the obtainment of the texture of the austenitic plus ferritic type, and in the 6^(th) layer (6), an adequate crystallization electrode for the obtainment of the bianitic type is used.

If the part being welded is thicker than 25 millimeters, the 1^(st) layer (1) is again applied with the deposited weld crystallization for the obtainment of the austenitic plus ferritic texture and, followed by the 2^(nd), 3^(rd), 4^(th), 5^(th) and 6^(th) layers (2, 3, 4, 5, 6) with the respective texture characteristics described above, until completing the filling of the bevel, it not being necessary to apply all 6 layers (1, 2, 3, 4, 5, 6) for the entire filling of the bevel, but it is essential to observe the order of application of the layers, as indicated above. The length of each weld bead should be approximately 10 cm of applied weld, as in an intermingled fashion, instead of continuous beads.

Summarizing, the purpose of the 1^(st) layer (1) is to cover the bevel and its root with the electrode of the deposited weld crystallization; which should be adequate for the obtainment of an austenitic plus ferretic texture. With the 2^(nd) layer (2), we proceed to fitting the bevel with the deposited weld crystallization, obtaining a pearalitic or pearalitic plus troostitic texture while, in the 3^(rd) and 5^(th) layers (3, 5), an electrode of deposited weld crystallization for the obtainment of an austenitic plus ferritic texture. In the 4^(th) layer (4), an electrode of deposited weld crystallization for the obtainment of a sorbitic plus bianitic texture is used, and in the 6^(th) layer (6), an electrode of deposited weld crystallization for the obtainment of the bainitic texture is used.

There being the necessity for more layers, successive layers are applied in the quantity necessary to fill in the bevel or in the desired volume, not necessarily corresponding to the volume of the bevel, and the layers applied do not necessarily have to have all of the 6 layers described above but need to obey the order of application established in the present invention.

After application of all the desired layers, then, when necessary, the milling of the piece may proceed for the recovery of its original dimensions, without the need of thermal treatment of the weld for the milling procedure.

The temperature of the part is limited to 100° C. using the procedure described, that is, intermingled welding, each bead having a length of more or less 10 cm, with the narrowest width possible.

Notwithstanding the present invention being illustrated in accordance with a concretization currently preferred, it is understood that this in no way limits the invention, since the alterations and modifications will be immediately evident to the experts, in light of the present exposition. For this reason, the invention shall be limited exclusively by the scope of the following claims. 

1) Process for capillary electric welding of low and high alloy steels, hardened or not, and bi-metals, for the obtainment of a determined texture, without thermal treatment, characterized by the fact of involving the use electrodes for capillary electric welding with specific properties for welding all types of steel, such as low and high alloy steels, both hardenable and hardened, high carbon steel or manganese steel (Hadfield), or SAE 4140 steel, the parts having been beveled according to the X, U or V bevel patterns, independent of their thickness, it being unnecessary to know the chemical composition of the material Of materials to be welded, as in the case of dissimilar parts such as bi-metals, through the definition of the following stages: starting with the welding of one piece (7), duly beveled, using a type of electrode with deposited austenitic plus ferritic weld crystallization texture, as follows: in the first layer (1), face both side of the bevel, including its root, using electrodes of adequate deposited weld crystallization for obtainment of the austenitic plus ferritic type texture, tacking both parts with the same electrode, to join them; in the second layer (2), electrodes of adequate deposited weld crystallization of pearlitic or pearlitic plus troostitic texture are used; in the third layer (3), electrodes of adequate deposited weld crystallization of austenitic texture are used, and in the fourth layer (4) electrodes of adequate deposited weld crystallization of sorbitic plus bainitic texture are used; in the fifth layer (5) electrodes of adequate deposited weld crystallization for the obtainment of an austenitic plus ferritic texture are used, and in the sixth layer (6), electrodes of adequate deposited weld crystallization for obtainment of a bainitic texture are used. 2) Process for capillary electric welding of low and high alloy steels, hardened or not, and bi-metals, for the obtainment of a determined texture, without normal treatment, in accordance with claim 1, characterized by the fact that, when a welded part presents a thickness greater than 25 millimeters, the first layer (1) is applied again with electrodes of deposited weld crystallization for the obtainment of a austenitic plus ferritic texture, then followed by the 2nd, 3rd, 4th, 5th and 6th layers (2, 3, 4, 5, 6), with the respective texture characteristics previously described, until completion of the bevel filling, it not being necessary to complete the application of all six layers (1,2,3,4, 5,6) for the total filling of the bevel, but it being imperative to observe the above specified order of application. 3) Process for capillary electric welding of low and high alloy steels, hardened or not, and bi-metals, for the obtainment of a determined texture, without thermal treatment, in accordance with claim 1, characterized by the fact that the length of each weld bead shall be of approximately 10 cm, in an intermingled manner, instead of uninterrupted beads. 4) Process for capillary electric welding of low and high alloy steels, hardened or not, and bi-metals, for the obtainment of a determined texture, without thermal treatment, in accordance with claim 1, characterized by the fact that after the application of all the layers desired, the part may be milled for recovery of its original dimensions, without the need of thermal treatment of the weld before undergoing the milling procedure. 5) Process for capillary electric welding of low and high alloy steels, hardened, or not, and bi-metals, for the obtainment of a determined texture, without thermal treatment, in accordance with claim 1, characterized by the fact that the temperature of the part is limited to a maximum of 100° C., through the use of the present welding procedure. 